Angularly adjustable intervertebral cages with integrated ratchet assembly

ABSTRACT

The embodiments provide various interbody fusion spacers, or cages, for insertion between adjacent vertebrae. The cages may have integrated ratchet assemblies that allow the cage to change size and angle as needed, with little effort. The cages may have a first, insertion configuration characterized by a reduced size to facilitate insertion through a narrow access passage and into the intervertebral space. The cages may be inserted in a first, reduced size and then expanded to a second, larger size once implanted. In their second configuration, the cages are able to maintain the proper disc height and stabilize the spine by restoring sagittal balance and alignment. Additionally, the intervertebral cages are configured to be able to adjust the angle of lordosis, and can accommodate larger lordotic angles in their second, expanded configuration. Further, these cages may promote fusion to further enhance spine stability by immobilizing the adjacent vertebral bodies.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 16/293,374filed Mar. 5, 2019, which claims the benefit of U.S. Patent ApplicationSer. No. 62/639,282 filed Mar. 6, 2018, the disclosure of each of whichis hereby incorporated by reference as if set forth in its entiretyherein.

TECHNICAL FIELD

The present disclosure relates to implantable orthopedic devices, andmore particularly to implantable devices for stabilizing the spine. Evenmore particularly, the present disclosure relates to angularlyadjustable intervertebral cages comprising integrated ratchet assembliesthat allow expansion of the cages from a first, insertion configurationhaving a reduced size to a second, implanted configuration having anexpanded size. The intervertebral cages are configured to adjust andadapt to lordotic angles, particularly larger lordotic angles, whilerestoring sagittal balance and alignment of the spine.

BACKGROUND

The use of fusion-promoting interbody implantable devices, oftenreferred to as cages or spacers, is well known as the standard of carefor the treatment of certain spinal disorders or diseases. For example,in one type of spinal disorder, the intervertebral disc has deterioratedor become damaged due to acute injury or trauma, disc disease or simplythe natural aging process. A healthy intervertebral disc serves tostabilize the spine and distribute forces between vertebrae, as well ascushion the vertebral bodies. A weakened or damaged disc thereforeresults in an imbalance of forces and instability of the spine,resulting in discomfort and pain. The standard treatment today mayinvolve surgical removal of a portion, or all, of the diseased ordamaged intervertebral disc in a process known as a partial or totaldiscectomy, respectively. The discectomy is often followed by theinsertion of a cage or spacer to stabilize this weakened or damagedspinal region. This cage or spacer serves to reduce or inhibit mobilityin the treated area, in order to avoid further progression of the damageand/or to reduce or alleviate pain caused by the damage or injury.Moreover, these types of cages or spacers serve as mechanical orstructural scaffolds to restore and maintain normal disc height, and insome cases, can also promote bony fusion between the adjacent vertebrae.

However, one of the current challenges of these types of procedures isthe very limited working space afforded the surgeon to manipulate andinsert the cage into the intervertebral area to be treated. Access tothe intervertebral space requires navigation around retracted adjacentvessels and tissues such as the aorta, vena cava, dura and nerve roots,leaving a very narrow pathway for access. The opening to the intradiscalspace itself is also relatively small. Hence, there are physicallimitations on the actual size of the cage that can be inserted withoutsignificantly disrupting the surrounding tissue or the vertebral bodiesthemselves.

Further complicating the issue is the fact that the vertebral bodies arenot positioned parallel to one another in a normal spine. There is anatural curvature to the spine due to the angular relationship of thevertebral bodies relative to one another. The ideal cage must be able toaccommodate this angular relationship of the vertebral bodies, or elsethe cage will not sit properly when inside the intervertebral space. Animproperly fitted cage would either become dislodged or migrate out ofposition, and lose effectiveness over time, or worse, further damage thealready weakened area.

Thus, it is desirable to provide intervertebral cages or spacers thatnot only have the mechanical strength or structural integrity to restoredisc height or vertebral alignment to the spinal segment to be treated,but also be configured to easily pass through the narrow access pathwayinto the intervertebral space, and then accommodate the angularconstraints of this space, particularly for larger lordotic angles.

BRIEF SUMMARY

The present disclosure includes spinal implantable devices that addressthe aforementioned challenges and meet the desired objectives. Thesespinal implantable devices, or more specifically intervertebral cages orspacers, are configured to be expandable as well as angularlyadjustable. The cages can include upper and lower plates for bearingagainst endplates of the vertebral bodies, and have integrated ratchetassemblies that allow the cage to change size and angle as needed, withlittle effort. In some embodiments, the cages may have a first orinsertion configuration characterized by a first height to facilitateinsertion through a narrow access passage and into the intervertebralspace. The cages may be inserted in the first or insertionconfiguration, and then expanded to a second expanded configurationcharacterized by a second height that is greater than the first height.In the second or expanded configuration, the cages are able to maintainthe proper disc height and stabilize the spine by restoring sagittalbalance and alignment. Additionally, the intervertebral cages areconfigured to be angularly adjustable to correspond to an angle oflordosis, and can accommodate larger lordotic angles in their second,expanded configuration. Further, the cages can promote fusion to furtherenhance spine stability by immobilizing the adjacent vertebral bodies.

According to one aspect of the disclosure, the cages may be manufacturedusing selective laser melting (SLM) techniques, a form of additivemanufacturing. The cages may also be manufactured by other comparabletechniques, such as for example, 3D printing, electron beam melting(EBM), layer deposition, and rapid manufacturing. With these productiontechniques, it is possible to create an all-in-one, multi-componentdevice which may have interconnected and movable parts without furtherneed for external fixation or attachment elements to keep the componentstogether. Accordingly, the intervertebral cages of the presentdisclosure are formed of multiple, interconnected parts that do notrequire additional external fixation elements to keep together.

Further, cages manufactured in this manner do not have connection seamswhereas devices traditionally manufactured have joined seams to connectone component to another. These connection seams can often representweakened areas of the implantable device, particularly when the bonds ofthese seams wear or break over time with repeated use or under stress.By manufacturing the disclosed implantable devices using additivemanufacturing, one of the advantages is that connection seams areavoided entirely and therefore the problem is avoided.

Another advantage of the present devices is that, by manufacturing thesedevices using an additive manufacturing process, all of the componentsof the device (that is, both the intervertebral cage and the pins forexpanding and blocking) can remain a complete construct during both theinsertion process as well as the expansion process. That is, multiplecomponents are provided together as a collective single unit so that thecollective single unit is inserted into the patient, actuated to allowexpansion, and then allowed to remain as a collective single unit insitu. In contrast to other cages requiring insertion of external screwsor wedges for expansion, in the present embodiments the expansion andblocking components do not need to be inserted into the cage, norremoved from the cage, at any stage during the process. This is becausethese components are manufactured so as to be captured internally withinthe cages, and while freely movable within the cage, are alreadycontained within the cage so that no additional insertion or removal isnecessary.

In some embodiments, the cages can have an engineered cellular structureon a portion of, or over the entirety of, the cage. This cellularstructure can include a network of pores, microstructures andnanostructures to facilitate osteosynthesis. For example, the engineeredcellular structure can comprise an interconnected network of pores andother micro and nano sized structures that take on a mesh-likeappearance. These engineered cellular structures can be provided byetching or blasting, to change the surface of the device on the nanolevel. One type of etching process may utilize, for example, HF acidtreatment.

In addition, these cages can also include internal imaging markers thatallow the user to properly align the device and generally facilitateinsertion through visualization during navigation. The imaging markershows up as a solid body amongst the mesh under x-ray, fluoroscopy or CTscan, for example.

Another benefit provided by the implantable devices of the presentdisclosure is that they can be specifically customized to the patient'sneeds. Customization of the implantable devices is relevant to providinga preferred modulus matching between the implant device and the variousqualities and types of bone being treated, such as for example, corticalversus cancellous, apophyseal versus central, and sclerotic versusosteopenic bone, each of which has its own different compression tostructural failure data. Likewise, similar data can also be generatedfor various implant designs, such as for example, porous versus solid,trabecular versus non-trabecular, etc. Such data may be cadaveric, orcomputer finite element generated. Clinical correlation with, forexample, DEXA data can also allow implantable devices to be designedspecifically for use with sclerotic, normal, or osteopenic bone. Thus,the ability to provide customized implantable devices such as the onesprovided herein allow the matching of the Elastic Modulus of ComplexStructures (EMOCS), which enable implantable devices to be engineered tominimize mismatch, mitigate subsidence and optimize healing, therebyproviding better clinical outcomes.

In one exemplary embodiment, an expandable spinal implant is provided.The expandable spinal implant may comprise a housing comprising an upperplate configured for placement against an endplate of a first vertebralbody and a lower plate configured for placement against an endplate of asecond, adjacent vertebral body. The expandable spinal implant mayfurther include an integrated ratchet assembly within the housing thatis configured to effect angular adjustment of the spinal implant. Theratchet assembly may comprise an enlarged head attached to a shafthaving a series of flanges, and a sleeve having a slotted opening forcapturing the shaft. In use, release of the shaft from the sleeveenables the enlarged head to urge against the upper and lower plates andcause angular adjustment of the plates relative to one another.

In accordance to one aspect of the embodiment, the housing may includeone or springs configured to control expansion of the sidewalls. Thesprings can be configured as deformable strips, and can extend from theupper plate to the lower plate. The upper and lower plates may connectto the housing by a cone hinge. The housing may include aninstrument-engaging opening. The housing may include a porous surface onat least one of the upper and lower surfaces.

In some examples, the housing can include more than one enlarged head.The implant may be configured for posterior lumbar interbody fusion(PLIF), or for anterior lumbar interbody fusion (ALIF).

In another exemplary embodiment, an expandable spinal implant caninclude a housing that includes an upper plate configured for placementagainst an endplate of a first vertebral body and a lower plateconfigured for placement against an endplate of a second, adjacentvertebral body. The expandable spinal implant may further include anintegrated ratchet assembly within the housing that is configured toeffect angular adjustment of the spinal implant. The ratchet assemblycan include an elastically deformable plate connecting the upper andlower plates. The elastically deformable plate can have an edgeconfigured to releasable engage a ratcheting pin, and a sleeve having aslotted opening for capturing the shaft. In use, the release of the pinfrom the sleeve allows the upper and lower plates to move apart andcause angular adjustment of the plates relative to one another.

In accordance to one aspect of the embodiment, the housing may include aporous surface. That porous surface may be on the upper or lower plate,or both. In some embodiments, a leading end of the implant is tapered.In addition, the housing may further include a bone graft window. Theratcheting pin may extend into an enlarged head for urging the upper andlower plates apart. The enlarged head may include a slot for engagingguide rails on the upper and lower plates. In addition, the upper andlower plates may further include steps for engaging the enlarged head.The implant may be configured for posterior lumbar interbody fusion(PLIF) or for anterior lumbar interbody fusion (ALIF).

Although the following discussion focuses on spinal implants, it will beappreciated that many of the principles may equally be applied to otherstructural body parts requiring bone repair or bone fusion within ahuman or animal body, including other joints such as knee, shoulder,ankle or finger joints.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the disclosure. Additional features of thedisclosure will be set forth in part in the description which follows ormay be learned by practice of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate several embodiments of thedisclosure and together with the description, serve to explain theprinciples of the disclosure.

FIG. 1A is a perspective front view of an intervertebral cageconstructed in accordance with one example, shown in an insertionconfiguration;

FIG. 1B is another perspective rear view of the intervertebral cageillustrated in FIG. 1A;

FIG. 1C is a side elevation view of the intervertebral cage illustratedin FIG. 1A;

FIG. 1D is a side view of the intervertebral cage illustrated in FIG.1A, shown in an expanded configuration;

FIG. 1E is an exploded perspective view of a portion of theintervertebral cage illustrated in FIG. 1A showing the connection ofupper and lower plates to a housing;

FIG. 1F is an exploded perspective view of a hinge constructed inaccordance with an alternative embodiment;

FIG. 2A is a perspective view of an intervertebral cage constructed inaccordance with another example, shown in an insertion configuration;

FIG. 2B is another perspective of the intervertebral cage illustrated inFIG. 2A;

FIG. 2C is a side view of the intervertebral cage illustrated in FIG.2A;

FIG. 2D is a side view of the intervertebral cage illustrated in FIG.2A, shown in an expanded configuration;

FIG. 2E is a perspective view of the intervertebral cage illustrated inFIG. 2D;

FIG. 2F is a perspective view of the intervertebral cage illustrated inFIG. 2E, with portions cut away;

FIG. 3 is a perspective rear view of an intervertebral cage constructedin accordance with another example;

FIG. 4A is a perspective view of an intervertebral cage constructed inaccordance with another embodiment, shown in an unexpanded, insertionconfiguration;

FIG. 4B is another perspective view of the intervertebral cageillustrated in FIG. 4A;

FIG. 4C is a cross-sectional perspective view of the intervertebral cageillustrated in FIG. 4A;

FIG. 4D is a sectional top view of the intervertebral cage illustratedin FIG. 4A;

FIG. 5 is a cross-sectional perspective view of an intervertebral cageconstructed in accordance with another example, shown in an unexpanded,insertion configuration; and

FIG. 6 is a cross-sectional perspective view of an intervertebral cagesimilar to the cage illustrated in FIG. 5, but including shallowerporous structures.

DETAILED DESCRIPTION

The present disclosure provides various spinal implant devices, such asinterbody fusion spacers, or cages, for insertion between adjacentvertebrae. The devices can be configured for use in either the cervicalor lumbar region of the spine. Thus, reference below to lordosis orlordotic angles can likewise apply to kyphosis or kyphotic angles. Insome embodiments, these devices may be configured as ALIF cages, or LLIFcages.

These cages can restore and maintain intervertebral height of the spinalsegment to be treated, and stabilize the spine by restoring sagittalbalance and alignment. In some embodiments, the cages may haveintegrated ratchet assemblies that allow the cage to change size andangle as needed, with little effort. The cages may have a first orinsertion configuration characterized by a first or reduced size tofacilitate insertion through a narrow access passage and into theintervertebral space. The cages may be inserted in the first orinsertion configuration, and then expanded to a second or expandedconfiguration having a second larger greater than the first or reducedsize once implanted. In one example, the size can be defined by aheight. In their second configuration, the cages are able to maintainthe proper disc height and stabilize the spine by restoring sagittalbalance and alignment. Additionally, the intervertebral cages areconfigured to be able to adjust the angle of lordosis, and canaccommodate larger lordotic angles in their second, expandedconfiguration. Further, these cages may promote fusion to furtherenhance spine stability by immobilizing the adjacent vertebral bodies.

Additionally, the implantable devices may be manufactured usingselective laser melting (SLM) techniques, a form of additivemanufacturing. The devices may also be manufactured by other comparabletechniques, such as for example, 3D printing, electron beam melting(EBM), layer deposition, and rapid manufacturing. With these productiontechniques, it is possible to create an all-in-one, multi-componentdevice which may have interconnected and movable parts without furtherneed for external fixation or attachment elements to keep the componentstogether. Accordingly, the intervertebral cages of the presentdisclosure are formed of multiple, interconnected parts that do notrequire additional external fixation elements to keep together.

Further, devices manufactured in this manner can be constructed withoutconnection seams, whereas devices traditionally manufactured includejoined seams to connect one component to another. These connection seamscan often represent weakened areas of the implantable device,particularly when the bonds of these seams wear or break over time withrepeated use or under stress. By manufacturing the disclosed implantabledevices using additive manufacturing, connection seams can be avoidedentirely and therefore the problem is avoided.

In addition, by manufacturing these devices using an additivemanufacturing process, all of the internal components of the deviceremain a complete construct during both the insertion process as well asthe expansion process. That is, multiple components are providedtogether as a collective single unit so that the collective single unitis inserted into the patient, actuated to allow expansion, and thenallowed to remain as a collective single unit in situ. In contrast toother cages requiring insertion of external screws or wedges forexpansion, in the present embodiments the expansion and blockingcomponents do not need to be inserted into the cage, nor removed fromthe cage, at any stage during the process. This is because thesecomponents are manufactured so as to be captured internally within thecages, and while freely movable within the cage, are already containedwithin the cage so that no additional insertion or removal is necessary.

In some embodiments, the cages can have an engineered cellular structureon a portion of, or over the entirety of, the cage. This cellularstructure can include a network of pores, microstructures andnanostructures to facilitate osteosynthesis. For example, the engineeredcellular structure can comprise an interconnected network of pores andother micro and nano sized structures that take on a mesh-likeappearance. These engineered cellular structures can be provided byetching or blasting, to change the surface of the device on the nanolevel. One type of etching process may utilize, for example, HF acidtreatment.

In addition, these cages can also include internal imaging markers thatallow the user to properly align the cage and generally facilitateinsertion through visualization during navigation. The imaging markershows up as a solid body amongst the mesh under x-ray, fluoroscopy or CTscan, for example.

Another benefit provided by the implantable devices of the presentdisclosure is that they can be specifically customized to the patient'sneeds. Customization of the implantable devices is relevant to providinga preferred modulus matching between the implant device and the variousqualities and types of bone being treated, such as for example, corticalversus cancellous, apophyseal versus central, and sclerotic versusosteopenic bone, each of which has its own different compression tostructural failure data. Likewise, similar data can also be generatedfor various implant designs, such as for example, porous versus solid,trabecular versus non-trabecular, etc. Such data may be cadaveric, orcomputer finite element generated. Clinical correlation with, forexample, DEXA data can also allow implantable devices to be designedspecifically for use with sclerotic, normal, or osteopenic bone. Thus,the ability to provide customized implantable devices such as the onesprovided herein allow the matching of the Elastic Modulus of ComplexStructures (EMOCS), which enable implantable devices to be engineered tominimize mismatch, mitigate subsidence and optimize healing, therebyproviding better clinical outcomes.

Turning now to the drawings, FIGS. 1A to 1E illustrate an example of anexpandable and angularly adjustable intervertebral cage 110 of thepresent disclosure. FIGS. 1A and 1B show the intervertebral cage 110 inits smaller, insertion configuration. The intervertebral cage 110 caninclude a housing 120 that defines an upper plate 130 and a lower plate140 that are configured to be placed against respective vertebralendplates of a pair of first and second adjacent vertebral bodies. Inparticular, the upper plate 130 can define an upper bearing surface 131configured to abut the vertebral endplate of the first vertebral body.Similarly, the lower plate 140 can define a lower bearing surface 141that is configured to abut the vertebral endplate of the secondvertebral body. The first vertebral body can define a superior vertebralbody, and the second vertebral body can define an inferior vertebralbody. The upper and lower plates 130 and 140 can be opposite each otheralong a transverse direction T.

The intervertebral cage 110 has a front or leading end 114 with respectto the direction of insertion into the intervertebral disc space. Theintervertebral cage 110 can further define a rear or trailing end 116that is opposite the leading end 114 along a longitudinal direction Lthat is oriented perpendicular to the transverse direction T. Theintervertebral cage 110 can define a length along the longitudinaldirection L and a width along a lateral direction A that isperpendicular to each of the longitudinal direction L and the transversedirection T.

The intervertebral cage 110 can define a forward or leading directionthat extends from the trailing end 116 toward the leading end 114. Thus,leading components of the intervertebral cage 110 can be spaced fromtrailing components of the intervertebral cage in the forward or leadingdirection. The intervertebral cage 110 can similarly define a rearwardor trailing direction that extends from the leading end 114 toward thetrailing end 116. In one embodiment, the leading end 114 can be tapered.For instance, one or both of the upper and lower plates 130 and 140 cantaper toward the other as they extend in the forward direction at theirrespective front or leading ends. In one example, the intervertebralcage 110 can be configured for posterior lumbar interbody fusion (PLIF).Thus, once implanted, the leading end 114 can define an anatomicallyanterior end of the cage 110, and the trailing end 116 can define ananatomically posterior end of the cage 110. The width of the cage 110can extend generally along the anatomical medial-lateral direction. Asshown, the upper and lower plates 130 and 140 may have a porousstructure 132 to facilitate cellular activity and bony ingrowth. Theporous structure 132 can define the upper and lower bearing surfaces 131and 141.

The intervertebral cage 110 can further include a hinge plate 122 thatextends between the upper and lower plates 130 and 140 together. Forinstance, the hinge plate 122 can extend between the upper and lowerplates 130 and 140 together at the rear of the housing 120. As shown inFIG. 1E, the upper and lower plates 130 and 140 can define a hinge withthe hinge plate 122. For instance, one of the hinge plate 122 and theupper plate 130 can define a concave surface, and the other of the hingeplate 122 and the upper plate can define a convex surface. Similarly,one of the hinge plate 122 and the lower plate 140 can define a concavesurface, and the other of the hinge plate 122 and the lower plate 140can define a convex surface. In one example, the hinge plate 122 candefine upper and lower convex surfaces, and the upper and lower plates130 and 140 can define respective upper and lower concave surfaces thatride along the upper and lower convex surfaces of the hinge plate 122,respectively, as the intervertebral cage articulates. Alternatively, thehinge plate 122 can be monolithic with one of the upper plate 130 andthe lower plate 140 so as to define a living hinge.

Referring to FIG. 1F, in another example the intervertebral cage 110 caninclude a cone hinge 154 that hingedly attaches the upper and lowerplates 130 and 140 to the housing 120. The cone hinge 154 can include aprinted hinge that comprises a first plate that defines a projection 156such as a cone or dome on one surface, and a second plate that defines aconcavity, such as a cup 158 that extends into one surface. One or bothof the first and second plates can be attached to the upper and lowerplates 130 and 140, such that the intervertebral cage 110 articulates inthe manner described herein.

With continuing reference to FIGS. 1A-1E generally, the intervertebralcage can further include at least one spring 150 that extends from theupper plate 130 to the lower plate 140. The spring 150 can apply aspring force against the upper and lower plates 140 that biases theupper and lower plates 130 and 140 toward the first or insertionconfiguration. Thus, the spring force can control movement of the upperand lower plates 130 and 140 relative to one another. It is appreciatedthat the upper and lower plates 130 and 140 are configured to overcomethe spring force and move relative to one another in the mannerdescribed herein. In one example, the spring 150 can be configured asone or more elastically deformable strips 150 that are connected attheir opposed free ends to the upper and lower plates 130 and 140,respectively.

The intervertebral cage 110 can further include an integrated ratchetassembly 160 that is fully integrated within the housing 120. Inparticular, the ratchet assembly 160 can be disposed between the upperand lower plates 130 and 140 with respect to the transverse direction T.The ratchet assembly 160 can include a ratchet shaft 164, and anengagement member 161 that is supported by the shaft 164 in the housing120 at a location between the upper and lower plates 130 and 140 withrespect to the transverse direction T. As will be described in moredetail below, engagement member can be moved in the forward direction tourge the upper and lower plates 130 and 140 away from each other alongthe transverse direction. In particular, the ratchet assembly 160operates by a pushing action, and in particular by pushing theengagement member 161 in the forward direction. The engagement member161 can be configured as an enlarged head 162 having a greatercross-section than the shaft 164. In particular, the engagement member161 can have a height that is greater than the distance between theupper and lower plates 130 and 140 along the transverse direction whenthe cage 110 is in its first or insertion configuration.

The shaft 164 can be elongated along the longitudinal direction L, andsupports the engagement member 161 at a forward end of the shaft 164.The ratchet assembly 160 can further include a plurality of flanges 166that extend out from the shaft 164 at a location rearward of theengagement member 161. The flanges 166 can be spaced from each otheralong the longitudinal direction L. As will be appreciated from thedescription below, the flanges 166 can define the ratchets of theratchet assembly 160. The ratchet assembly 160 can further include asleeve 170 that at least partially surrounds the shaft 164. When theratchet assembly 160 is in a first or initial position, the flanges 166can be disposed in the sleeve 170. Alternatively, one or more of theflanges 166 can be disposed forward of the sleeve 170. The sleeve 170can have a flexible front opening 172 at a longitudinally front end ofthe sleeve 170.

In particular, the front end 171 of the sleeve 170 that defines thefront opening 172 can be sized to receive the shaft 164, which canextend out of the sleeve in the forward direction through the frontopening 172. The front end 171 of the sleeve 170 can be sized smallerthan the outer cross-sectional dimension of the flanges 166 in a planethat is oriented perpendicular to the longitudinal direction L. Thefront end 171 of the sleeve 170 can be resiliently flexible, andconfigured to flex outward so as to allow the flanges 166 to movethrough the front opening 172 and out of the sleeve as the shaft 164 ismoved forward along the longitudinal direction L. Thus, the flanges 166ratchet through the front end 171 of the sleeve 170. In particular, thefront end 171 of the sleeve 170 can flex around the flanges 166 as theyare driven through the front opening 172. Thus, the flanges 166 canone-by-one (i.e., stepwise) be driven through the opening 172 at thefront end 171 of the sleeve 170 in the forward direction. In oneexample, the front end 171 can be slotted and tapered inwardly as itextends in the forward direction. The shaft 164 defines a longitudinallyrear end that is configured to engage an actuation instrument, which canalso provide an insertion instrument. For instance, the longitudinallyrear end of the sleeve 170 can be configured to receive the instrument.

As shown in FIG. 1B, the connection plate 122 can also include alongitudinal instrument-receiving opening 124. Thus, a dedicatedinstrument 190 can be inserted through the opening 124, and coupled tothe integrated ratchet assembly 160 so as to deploy the ratchet assembly160 within the housing 120. In particular, the instrument 190 can beinserted through the instrument-engaging opening 124 of the connectionplate 122 until it engages the sleeve 170, as shown in FIGS. 1C and 1D.The instrument 190 can be configured to drive the shaft 164 in theforward direction. For instance, an inner pin of the instrument 190 canextend forward through an opening in the rear end of the sleeve 170, andapply a force against the shaft 164 that urges the shaft 164 to travelin the forward direction.

Referring to FIG. 1D, as the shaft 164 travels in the forward direction,the flanges 166 move through the front opening 172 and out the sleeve170 in the manner described above. Each of the flanges 166 can define afirst or front surface 173 and a second or rear surface 175 opposite thefront surface 173 along the longitudinal direction L. The front surface173 can be beveled to facilitate insertion of the flanges 166 throughthe front opening 172 of the sleeve 170. In particular, the frontsurfaces 173 can flare rearwardly as they extend out from the shaft 164.The rear surfaces 175 can extend out from the shaft 164 along adirection substantially perpendicular to the central axis of the shaft164. Thus, the rear surface 175 is configured to abut the front end 171of the sleeve 170 when the shaft 164 is urged to move in the rearwarddirection. Abutment of the rear surface 175 against the front end of thesleeve 170 prevents the flanges 166 from being inserted into the sleeve170 in the rearward direction. Thus, the rear surfaces 175 of theflanges 166 provide a stop surface that prevents movement of the shaft164 in the rearward direction. Accordingly, the ratchet assembly 160 canbe configured to permit forward movement of the shaft 164, but preventrearward movement of the shaft 164. Alternatively, if desired, theflanges 166 can be configured to be driven through the opening 172 atthe front end 171 of the sleeve in the rearward direction.

As the shaft 164 moves in the forward direction, which can be referredto as an expansion direction, the engagement member 161 moves with theshaft 164 in the forward direction. Thus, the engagement member 161moves toward the front end 114 of the intervertebral cage 110. As theengagement member 161 moves in the forward direction at the front end114 of the intervertebral cage 110, the engagement member 161 contactsrespective transverse inner surfaces of each of the upper plate 130 andthe lower plate 140. Because the transverse inner surfaces of at leastone or both of the upper and lower plates 130 and 140 tapers toward theother along the transverse direction T in the manner described above,contact between the engagement member 161 and the upper and lower plates130 and 140 urges the front ends of the upper and lower plates 130 and140 to move away from each other along the transverse direction T. Theengagement member 161 can have a sloped profile, and can be configuredas a wedge as it forces the upper and lower plates 130 and 140 apartalong the transverse direction T as it moves in the forward direction.

As described above, the upper and lower plates 130 and 140 can behingedly fixed to each other at their respective rear ends. Thus, as thefront ends of the upper and lower plates 130 and 140 move away from eachother, the intervertebral cage 110 can assume a second or expandedconfiguration having a height at the front end that is greater than theheight of the cage 110 in the first or insertion configuration. Theheight is measured along the transverse direction T. Further, the cage110 can angulate as it expands from the first or insertion configurationto the second or expanded configuration. That is, the upper and lowerplates 130 and 140 can define a first relative angular orientation whenthe cage 110 is in the first or initial configuration. The upper andlower plates 130 and 140 can define a second relative angularorientation when the cage 110 is in the second or expandedconfiguration. The second relative angular orientation can be differentthan the first relative angular orientation. The first and secondrelative angular orientations can be measured in a plane that isoriented along the longitudinal direction L and the transverse directionT. In one example, the upper and lower plates 130 and 140 can angulateabout the hinge 154.

The cage 110 can be expanded along the transverse direction T andangulated in increments as the flanges 166 are driven out of the frontend 171 of the sleeve 170. The closer the flanges 166 are spaced apartalong the longitudinal direction L, the smaller the increments will beduring expansion and angulation as the flanges 166 are individuallydriven out of the front end 171. Conversely, the further that theflanges 166 are spaced apart along the longitudinal direction L, thegreater the increments will be during expansion and angulation as theflanges 166 are individually driven out of the front end 171. Thus, thecage 110 may be printed in one run, and provide small incrementaladjustment of the height and angulation of the cage 110. The flanges 166can be equidistantly spaced along the shaft 164 or variably spaced alongthe shaft 164. The shaft 164 can be prevented from translatingrearwardly in response to compressive anatomical loads applied to thecage 110 along the transverse direction T during use.

As described above, the intervertebral cage 110 can be configured forposterior lumbar interbody fusion (PLIF), and the shaft 164 can bepushed in the forward direction by the instrument 190 so as to actuatethe intervertebral cage 110 from the first or insertion configuration tothe second or expanded configuration. It is understood, however, thatthe intervertebral cage 110 can be configured for anterior lumbarinterbody fusion (ALIF). As described in more detail below, when theintervertebral cage 110 is configured as an ALIF cage, the ratchetassembly 160 can be actuated by pulling the shaft 164 in the forwarddirection.

The intervertebral cage 110 can have any suitable dimension as desired.In one example where the cage 110 is configured as a PLIF cage, thedimensions can be any one of 22×9, 26×9, 30×9, 34×9, 22×11, 26×11, and30×11 (Length×Width), with the stated dimensions in mm. Thus, the lengthof the cage 110 along the longitudinal direction L can be in a rangefrom approximately 22 mm to approximately 34 mm, including any one ofapproximately 22 mm, approximately 26 mm, approximately 30 mm, andapproximately 34 mm. The term “approximate” recognizes manufacturingtolerances and other potential variations, and includes plus or minus10% of the stated number. The width of the cage 110 along the lateraldirection A can be in a range from approximately 9 mm to approximately11 mm. The height of the cage 110 from the upper bearing surface 131 tothe lower bearing surface 141 along the transverse direction can rangefrom approximately 7 mm to approximately 16 mm, in 1 mm increments, whenthe cage 110 is in the first or insertion configuration. Further, as thecage expands from the first configuration to the second configuration,the cage 110 can angulate in a range from approximately zero degrees toapproximately 18 degrees, including approximately 4 degrees,approximately 6 degrees, and approximately 12 degrees. As describedabove, the leading end 114 can be expanded along the transversedirection relative to the trailing end 116 as the cage 110 expands andangulates. It should be appreciated that the above values are presentedas examples only, and that the cage 210 can alternatively be configuredas desired.

FIGS. 2A to 2F illustrate another example of an intervertebral cage 210.The cage 210 shares similar features described above with respect to thecage 110, but is configured for an anterior lumbar interbody fusion(ALIF). FIGS. 2A and 2B show the intervertebral cage 210 in its smaller,insertion configuration. As described above with respect to the cage110, the intervertebral cage 210 can include a housing 220 that thatdefines an upper plate 230 and a lower plate 240 that are configured tobe placed against the respective vertebral endplates. In particular, theupper plate 230 can define an upper bearing surface 231 configured toabut the vertebral endplate of the first vertebral body. Similarly, thelower plate 140 can define a lower bearing surface 241 that isconfigured to abut the vertebral endplate of the second vertebral body.The upper and lower plates 230 and 240 can be opposite each other alonga transverse direction T.

The intervertebral cage 210 has a front or leading end 214 with respectto the direction of insertion into the intervertebral disc space. Theintervertebral cage 210 can further define a rear or trailing end 216that is opposite the leading end 214 along a longitudinal direction Lthat is oriented perpendicular to the transverse direction T. Theintervertebral cage 210 can define a length along the longitudinaldirection L and a width along a lateral direction A that isperpendicular to each of the longitudinal direction L and the transversedirection T.

The intervertebral cage 210 can define a forward or leading directionthat extends from the trailing end 216 toward the leading end 214. Thus,leading components of the intervertebral cage 210 can be spaced fromtrailing components of the intervertebral cage in the forward or leadingdirection. The intervertebral cage 210 can similarly define a rearwardor trailing direction that extends from the leading end 214 toward thetrailing end 216. In one embodiment, the leading end 214 can be tapered.In one example, the intervertebral cage 210 can be configured forposterior lumbar interbody fusion (ALIF). Thus, once implanted, theleading end 214 can define an anatomically posterior end of the cage210, and the trailing end 216 can define an anatomically anterior end ofthe cage 210. The width of the cage 210 can extend generally along theanatomical medial-lateral direction. As shown, the upper and lowerplates 230 and 240 may have a porous structure 232 to facilitatecellular activity and bony ingrowth. The porous structure 232 can definethe upper and lower bearing surfaces 231 and 241.

The intervertebral cage 210 can further include a rear plate 222 thatextends from one of the upper plate 230 and the lower plate 240. In oneexample, the rear plate 222 can extend up from the lower plate 240 atthe trailing end 216 of the cage 210. Further, the leading end of thecage 210 can include a hinge plate that extends between the upper plate230 and the lower plate 240 at the leading end 214 of the cage 210. Thehinge plate can be constructed as described above with respect to thehinge plate 122. Alternatively, the hinge plate can be monolithic withone or both of the upper and lower plates 230 and 240 so as to defineone or more living hinges. For instance, the connection plate 222 canconnect the upper and lower plates 230 and 240 together at the front ofthe housing 220. In addition, referring also to FIG. 2C, theintervertebral cage 210 can further include at least one spring 250 thatextends from the upper plate 230 to the lower plate 240. The spring 250can apply a spring force against the upper and lower plates 230 and 240that biases the upper and lower plates 230 and 240 toward the first orinsertion configuration. Thus, the spring force can control movement ofthe upper and lower plates 230 and 240 relative to one another. It isappreciated that the upper and lower plates 230 and 240 are configuredto overcome the spring force and move relative to one another in themanner described herein. In one example, the spring 250 can beconfigured as one or more elastically deformable strips 250 that areconnected at their opposed free ends to the upper and lower plates 230and 240, respectively. In one example, each lateral side of the cage 210can include a pair of deformable strips that are positioned adjacenteach other and are mirror images of each other.

Referring now also to FIG. 2F, the intervertebral cage 110 can furtherinclude an integrated ratchet assembly 260 that is fully integratedwithin the housing 220. In particular, the ratchet assembly 260 can bedisposed between the upper and lower plates 230 and 240 with respect tothe transverse direction T. The ratchet assembly 160 can include atleast one ratchet shaft 264 and at least one engagement member 261 thatis supported by the shaft 264 in the housing 220 at a location betweenthe upper and lower plates 230 and 240 with respect to the transversedirection T. For instance, the ratchet assembly 260 can include firstand second engagement shafts 264 and first and second members 261 thatare supported by respective ones of the shafts 264. The engagementmembers 261 can be spaced from each other along the lateral direction A.The first and second engagement members 261 can be equidistantly spacedfrom the longitudinal central axis of the cage 210, or can be otherwisepositioned as desired. It should be appreciated that the ratchetassembly 160 described above can similarly include first and secondengagement members 161 as described herein with respect to the ratchetassembly 260. Alternatively, the ratchet assembly 260 can include asingle engagement member 261 as described above with respect to theratchet assembly 160.

As will be described in more detail below, the engagement members 261can be moved in the rearward direction to urge the upper and lowerplates 230 and 240 away from each other along the transverse directionT. In particular, the ratchet assembly 260 can operates by a pullingaction, and in particular by pulling the engagement members 261 in therearward direction toward the trailing end 216. The engagement members161 can be configured as enlarged heads 162 having a greatercross-section than the shaft 264. In particular, the engagement members261 can have a height that is greater than the distance between theupper and lower plates 230 and 240 along the transverse direction T whenthe cage 210 is in its first or insertion configuration.

The shafts 264 can be elongate along the longitudinal direction L, andcan support the engagement members 261 at respective rear ends of theshaft 264. The ratchet assembly 260 can further include a plurality offlanges 266 that extend out from each of the shafts 264 at a locationforward of the engagement member 261. The flanges 266 can be spaced fromeach other along the longitudinal direction L. As will be appreciatedfrom the description below, the flanges 266 can define the ratchets ofthe ratchet assembly 260. The ratchet assembly 260 can further includefirst and second sleeves 170 that at least partially surroundsrespective ones of the shafts 264. When the ratchet assembly 260 is in afirst or initial position, the flanges 266 can be disposed in thesleeves 270. Alternatively, one or more of the flanges 266 can bedisposed rearward of the sleeve 270. The sleeves 270 can have a flexiblefront opening 272 at a longitudinally rear end 271 of the sleeves 270.The rear end 271 of the sleeves 270 can be constructed as describedabove with respect to the front end 171 of the sleeve 170.

As shown in FIGS. 2B-2C, the rear plate 222 can also include alongitudinal instrument-receiving opening 224. Thus, a dedicatedinstrument 290 can be inserted through the opening 224, and coupled tothe integrated ratchet assembly 260 so as to deploy the ratchet assembly260 within the housing 220. In particular, the instrument 290 can beinserted through the instrument-engaging opening 224 of the rear plate222 until it engages the sleeve 270. The ratchet assembly 260 canfurther include a pull bar 280 that extends from the first shaft 264 orsupported actuation member 261 to the second shaft 164 or supportedactuation member 261 generally along the lateral direction A. Theinstrument 290 can be configured to engage the pull bar 280 so as todrive each of the shafts 264 and supported engagement members 261 in therearward direction in a pulling motion.

Referring to FIG. 1D, as the shafts 264 travel in the rearwarddirection, the flanges 266 move through the front openings 272 of therespective sleeve 270 and out the respective sleeve 270 in the mannerdescribed above. Each of the flanges 266 can define a first or rearsurface 273 and a second or front surface 275 opposite the rear surface273 along the longitudinal direction L. The rear surface 273 can bebeveled to facilitate insertion of the flanges 266 through the frontopenings 272 of the sleeves 270. In particular, the rear surfaces 273can flare forwardly as they extend out from the shaft 264. The frontsurfaces 275 can extend out from the shaft 264 along a directionsubstantially perpendicular to the central axis of the shaft 264. Thus,the front surfaces 275 are configured to abut the rear ends 271 of therespective sleeves 270 when the shaft 264 is urged to move in therearward direction. Abutment of the front surface 275 against the frontend of the sleeve 270 prevents the flanges 266 from being inserted intothe sleeve 270 in the forward direction. Thus, the front surfaces 275 ofthe flanges 266 provide a stop surface that prevents movement of theshaft 164 in the forward direction that would collapse the cage 210 onceexpanded. Accordingly, the ratchet assembly 260 can be configured topermit rearward movement of the shaft 264, but prevent forward movementof the shaft 264. Alternatively, if desired, the flanges 266 can beconfigured to be driven through the opening 272 at the front end 271 ofthe respective sleeve 270 in the forward direction.

As the shafts 264 move in the rearward direction, which can be referredto as an expansion direction, the engagement members 261 moves with theshaft 264 in the rearward direction. Thus, the engagement members 261moves toward the rear end 214 of the intervertebral cage 210. As theengagement members 261 move in the rearward direction at the rear end141 of the intervertebral cage 110, the engagement members 161 contactrespective transverse inner surfaces 235 and 245, respectively, of eachof the upper plate 230 and the lower plate 240. One or both of thetransverse inner surfaces 235 and 245 can taper toward the other of thetransverse inner surfaces 235 and 245 along the transverse direction Tas they extend in the rearward direction. In one example, the uppertransverse surface 235 can taper more than the lower transverse surface245. It should be appreciated, of course, that the transverse innersurfaces 235 and 245 can alternatively taper equally, or one can taperwhile the other does not.

It should thus be appreciated that the distance between the transverseinner surfaces 235 and 245 along the transverse direction T decreases asthe transverse inner surfaces 235 and 245 extend in the rearwarddirection. Accordingly, contact between the engagement members 161 andthe transverse inner surfaces 235 and 245 urges the rear ends of atleast one or both of the upper and lower plates 230 and 240 to move awayfrom the other of the upper and lower plates 230 and 240 along thetransverse direction T, thereby expanding the cage 210. The engagementmembers 261 can each have a sloped profile, and can be configured as awedge as it forces one or both of the upper and lower plates 230 and 240apart along the transverse direction T as it moves in the rearwarddirection.

As described above, the upper and lower plates 230 and 240 can behingedly fixed to each other at their respective rear ends. Thus, as therear ends of the upper and lower plates 230 and 240 move away from eachother, the intervertebral cage 210 can assume a second or expandedconfiguration having a height that is greater than the height of thecage 210 in the first or insertion configuration. The height is measuredalong the transverse direction T. Further, the cage 210 can angulate asit expands from the first or insertion configuration to the second orexpanded configuration. That is, the upper and lower plates 230 and 240can define a first relative angular orientation when the cage 210 is inthe first or initial configuration. The upper and lower plates 230 and240 can define a second relative angular orientation when the cage 210is in the second or expanded configuration. The second relative angularorientation can be different than the first relative angularorientation. The first and second relative angular orientations can bemeasured in a plane that is oriented along the longitudinal direction Land the transverse direction T. In one example, the upper and lowerplates 230 and 240 can angulate about the hinge 254.

The cage 210 can be expanded along the transverse direction T andangulated in increments as the flanges 266 are driven out of the opening272 at the rear end 271 of the sleeve 270. The closer the flanges 266are spaced apart along the longitudinal direction L, the smaller theincrements will be during expansion and angulation as the flanges 266are individually driven out of the front end 271. Conversely, thefurther that the flanges 266 are spaced apart along the longitudinaldirection L, the greater the increments will be during expansion andangulation as the flanges 266 are individually driven out of the frontend 271. Thus, the cage 210 may be printed in one run, and provide smallincremental adjustment of the height and angulation of the cage 210. Theflanges 166 can be equidistantly spaced along the respective shafts 164or variably spaced along the respective shafts 164. The shafts 264 canbe prevented from translating along a forward direction, also referredto as a contraction direction, in response to compressive anatomicalloads applied to the cage 210 along the transverse direction T duringuse.

As described above, the intervertebral cage 110 can be configured foranterior lumbar interbody fusion (ALIF), and the shafts 264 can bedriven in the rearward direction by the instrument 290 so as to actuatethe intervertebral cage 210 from the first or insertion configuration tothe second or expanded configuration. It is understood, however, thatthe intervertebral cage 210 can be configured for posterior lumbarinterbody fusion (PLIF), in which case the ratchet assembly 160 can beactuated by driving the shafts 264 in the forward direction as describedabove with respect to the cage 110.

The intervertebral cage 210 can have any suitable dimension as desired.In one example where the cage 210 is configured as a ALIF cage, thedimensions can be any one of 34×25 37×27, 40×29, 45×32 (Length×Width),with the stated dimensions in mm. Thus, the length of the cage 210 alongthe longitudinal direction L can be in a range from approximately 34 mmto approximately 45 mm, including any one of approximately 34 mm,approximately 37 mm, approximately 40 mm, and approximately 45 mm. Theterm “approximate” recognizes manufacturing tolerances and otherpotential variations, and includes plus or minus 10% of the statednumber. The width of the cage 210 along the lateral direction A can bein a range from approximately 25 mm to approximately 32 mm. The heightof the cage 210 from the upper bearing surface 231 to the lower bearingsurface 241 along the transverse direction can range from approximately8 mm to approximately 20 mm, in 1 mm increments, when the cage 210 is inthe first or insertion configuration. Further, as the cage expands fromthe first configuration to the second configuration, the cage 210 canangulate in a range from approximately zero degrees to approximately 20degrees, including approximately 5 degrees, approximately 10 degrees,approximately 15 degrees, and approximately 20 degrees. As describedabove, the trailing end 216 can be expanded along the transversedirection relative to the leading end 214 as the cage 210 expands andangulates. It should be appreciated that the above values are presentedas examples only, and that the cage 210 can alternatively be configuredas desired.

FIG. 3 illustrates yet another exemplary embodiment of an intervertebralcage 310 of the present disclosure. The intervertebral cage 310 can beconstructed as described above with respect to each of the cages 110 and210. In FIG. 3, reference numerals corresponding to like elements ofthose described above have been incremented by 100 or 200 for thepurposes of clarity and convenience. The cage 310 can have a housing 320that includes upper and lower plates 330, 340 that are connected to thehousing 320 by a plate 322, and has an integrated ratchet assemblyconfigured to expand the cage 310. The integrated ratchet assembly canbe constructed as described above with respect to either of the ratchetassembly 160 or the ratchet assembly 260. Further, the cage 310 can bean ALIF cage, a PLIF cage, or any suitable alternatively configuredcage. In some examples, such as the one shown, one or both of the upperand lower plates 330 and 340 do not contain the porous structuredescribed herein. Thus, the corresponding one or both of the upper andlower bearing surfaces 331 and 341 of the upper and lower plates 330 and340, respectively, are not defined by a porous structure in someexamples. Instead, the corresponding one or both of the upper and lowerbearing surfaces 331 and 341 can be substantially smooth and continuousfrom the leading end to the trailing end of the cage along thelongitudinal direction L, and from a first lateral side to a secondlateral side of the cage 310 along the lateral direction A.

FIGS. 4A to 4D illustrate still another example of an intervertebralcage 410 of the present disclosure. FIGS. 4A and 4B show theintervertebral cage 410 in its smaller, insertion configuration. InFIGS. 4A-4D, reference numerals corresponding to like elements of thosedescribed above have been incremented by 100, 200, or 300 for thepurposes of clarity and convenience. The intervertebral cage 410 maycomprise a housing 420 defined by a pair of plates 430 and 440configured for placement against endplates of a pair of adjacentvertebral bodies. As shown, the plates 430 and 440 may have a porousstructure 432 to facilitate cellular activity and bony ingrowth in themanner described above.

The plates 430 and 440 are connected together at the rear end 416 of thehousing 420 by an elastic interconnection 450. The elasticinterconnection 450 can be defined by an elastic interconnected plate452 that is disposed between the plates 430 and 440. In particular, theelastic interconnected plate 452 can define one or more longitudinallyextending arms that can be configured to resiliently flex as the cage410 expands. Thus, the arms can define a biasing force that urges thecage 410 toward its first configuration. The arms of the interconnectedplate 452 can define an opening that receives a ratchet shaft 464. Theupper and lower plates 430 and 440 and the interconnected plate 452 candefine a single monolithic structure. The ratchet shaft 464 can bedriven in the expansion direction, which causes the ratchet shaft 464 toride along inner ramps of the upper and lower plates 430 and 440,thereby expanding the cage 410. In one example, the ratchet shaft 464can push the respective front ends of the upper and lower plates 430 and440 away from each other as it rides over the inner ramps, therebycausing the cage 410 to angulate. In particular, the leading end 414 ofthe cage 410 expands along the transverse direction T relative to thetrailing end 416. Thus, engagement between each of the upper and lowerplates 430 and 440 and the ratchet shaft 464 prevents the flexible armsof the interconnected plate 452 from driving the cage 410 to the firstconfiguration. The cage 410 can be a PLIF cage, and thus the expansiondirection can be defined by the forward direction. It should beappreciated, of course, that the cage 410 can alternatively beconfigured as an ALIF cage, in which case the expansion direction wouldbe defined by the rearward direction. The flanges 466 that extend outfrom the shaft 464 can cooperate with the tapered open end 472 of thesleeve 470 in the manner described above. The opposed rear end of thesleeve 270 can be secured within the housing 420.

The elastic interconnected plate 452 can define at least one an inwardlyprojecting tooth 465, such as an upper and lower tooth 465 that engageswith the flanges 466 of the ratchet assembly. Accordingly, as the shaft464 is incrementally driven out of the open end 472 of the sleeve 470 inthe expansion direction, the elastic interconnected plate 452 islikewise incrementally driven in the expansion direction, which is theforward direction as illustrated, which thereby allows theinterconnected plates 430 and 440 to expand in increments along thetransverse direction T as described above. As the cage 410 expands fromthe first configuration to the second configuration, the cage 410 canangulate in a range from approximately zero degrees to approximately 18degrees, including approximately 4 degrees, approximately 8 degrees,approximately 12 degrees, and approximately 16 degrees, as one example.

FIG. 5 illustrates yet still another example of an intervertebral cageof the present disclosure. In FIG. 5, reference numerals correspondingto like elements of those described above have been incremented by 100,200, 300, or 400 for the purposes of clarity and convenience. As shown,the intervertebral cage 510 shares similar features to intervertebralcage 410, but now also has more engineered porous structures 522 tomaximize the porous nature of the cage 510. In some example, the porousstructure 522 can have a thickness that ranges from approximately 0.5 mmto approximately 1 mm, though it should be appreciated that the porousstructure can have any suitable thickness as desired. Further, in someexample, the thickness of the porous structure 522 can range fromapproximately 1/10 and approximately ⅔ the height of the plate thicknessalong the transverse direction T. As described herein with respect tothe other cages, the cage 510 includes a housing 520 having an upperplate 530 and lower plate 540, and an elastic interconnection thatconnects the upper and lower plates 530 and 540 together at the rear end516 of the housing 520. The cage 510 can further include a bone graftwindow 528 that extends through one or both of the upper plate 530 andthe lower plate 450. The window 528 of the upper plate 530 can bealigned with the window 528 of the lower plate 540 along the transversedirection T.

As described above with respect to the other cages, the cage 510 caninclude a plurality of flanges 566 that extend out from the ratchetshaft 564. The engagement member 561, which can be configured as anenlarged head 562, extends out from the shaft 564 at a location spacedfrom the flanges 566 in the expansion direction. One or both of theupper and lower plates 530 and 540 can include a guide rail 529 thatextends along the longitudinal direction L. The guide rail 529 canextend from the transverse inner surface 535 and 545 of one or both ofthe upper and lower plates 530 and 540. The engagement member 561 caninclude a guide slot 567 that extends through the engagement member 561along the longitudinal direction L, and is sized to receive the guiderail 529, such that the engagement member 561 travels along the guiderail 529 as the shaft 564 is driven in the expansion direction. Itshould be appreciated that any of the ratchet assemblies describedherein can include a guide rail that is received in a guide slot of therespective engagement member.

Further, the inner transverse surface 535 and 545 of one or both of theupper and lower plates 530 and 540, respectively, can define a pluralityof steps 557. The steps 557 can be arranged so as to extend transverselyinward as they extend along the expansion direction. The steps canfurther be sized to receive the engagement member 561 as it travels inthe direction of expansion. Thus, each step 557 can define a seatagainst which the engagement member 561 can rest as it expands the cage510 beyond the first or insertion configuration. As the engagementmember 561 travels further in the expansion direction, the engagementmember 561 can rest on successively spaced steps 557 in the expansiondirection, thereby incrementally expanding and angulating the cage 510.The steps 557 and the flanges 566 can be spaced apart along thedirection a suitable distance such that the engagement member 561 canrest against the steps 557 while the open end of the 572 of the sleeve570 is disposed between adjacent flanges 566.

FIG. 6 illustrates further still another example of an intervertebralcage of the present disclosure. As shown, the intervertebral cage 610includes the features of the intervertebral cage 510. Thus, in FIG. 6,reference numerals corresponding to like elements of the cage 510 ofFIG. 5 have been incremented by 100 for the purposes of clarity andconvenience. As illustrated in FIG. 6, the porous structures 622 canhave a reduced thickness with respect to the porous structures 522illustrated in FIG. 5. Alternatively, the upper and lower bearingsurfaces 631 and 641 can be devoid of the porous structures as describedabove with respect to FIG. 3.

As mentioned above, the intervertebral cages of the present disclosureare configured to be able to allow insertion through a narrow accesspath, but are able to be expanded and angularly adjusted so that thecages are capable of adjusting the angle of lordosis of the vertebralsegments. By being able to angularly adjust and expand (or distract),the cages allow a very narrow anterior for insertion and a largeranterior after implantation to accommodate and adapt to larger angles oflordosis. Additionally, the cages can effectively restore sagittalbalance and alignment of the spine, and can promote fusion to immobilizeand stabilize the spinal segment.

With respect to the ability of the expandable cages to promote fusion,many in-vitro and in-vivo studies on bone healing and fusion have shownthat porosity is necessary to allow vascularization, and that thedesired infrastructure for promoting new bone growth should have aporous interconnected pore network with surface properties that areoptimized for cell attachment, migration, proliferation anddifferentiation. At the same time, there are many who believe theimplant's ability to provide adequate structural support or mechanicalintegrity for new cellular activity is the main factor to achievingclinical success, while others emphasize the role of porosity as the keyfeature. Regardless of the relative importance of one aspect incomparison to the other, what is clear is that both structural integrityto stabilize, as well as the porous structure to support cellulargrowth, are key components of proper and sustainable bone regrowth.

Accordingly, these cages may take advantage of current additivemanufacturing techniques that allow for greater customization of thedevices by creating a unitary body that may have both solid and porousfeatures in one. In some embodiments as shown, the cages can have aporous structure, and be made with an engineered cellular structure thatincludes a network of pores, microstructures and nanostructures tofacilitate osteosynthesis. For example, the engineered cellularstructure can comprise an interconnected network of pores and othermicro and nano sized structures that take on a mesh-like appearance.These engineered cellular structures can be provided by etching orblasting to change the surface of the device on the nano level. One typeof etching process may utilize, for example, HF acid treatment. Thesesame manufacturing techniques may be employed to provide these cageswith an internal imaging marker. For example, these cages can alsoinclude internal imaging markers that allow the user to properly alignthe cage and generally facilitate insertion through visualization duringnavigation. The imaging marker shows up as a solid body amongst the meshunder x-ray, fluoroscopy or CT scan, for example. A cage may comprise asingle marker, or a plurality of markers. These internal imaging markersgreatly facilitate the ease and precision of implanting the cages, sinceit is possible to manufacture the cages with one or more internallyembedded markers for improved visualization during navigation andimplantation.

Another benefit provided by the implantable devices of the presentdisclosure is that they are able to be specifically customized to thepatient's needs. Customization of the implantable devices is relevant toproviding a preferred modulus matching between the implant device andthe various qualities and types of bone being treated, such as forexample, cortical versus cancellous, apophyseal versus central, andsclerotic versus osteopenic bone, each of which has its own differentcompression to structural failure data. Likewise, similar data can alsobe generated for various implant designs, such as for example, porousversus solid, trabecular versus non-trabecular, etc. Such data may becadaveric, or computer finite element generated. Clinical correlationwith, for example, DEXA data can also allow implantable devices to bedesigned specifically for use with sclerotic, normal, or osteopenicbone. Thus, the ability to provide customized implantable devices suchas the ones provided herein allow the matching of the Elastic Modulus ofComplex Structures (EMOCS), which enable implantable devices to beengineered to minimize mismatch, mitigate subsidence and optimizehealing, thereby providing better clinical outcomes.

A variety of spinal implants may be provided by the present disclosure,including interbody fusion cages for use in either the cervical orlumbar region of the spine. Although only a posterior lumbar interbodyfusion (PLIF) device is shown, it is contemplated that the sameprinciples may be utilized in a cervical interbody fusion (CIF) device,a transforaminal lumbar interbody fusion (TLIF) device, anterior lumbarinterbody fusion (ALIF) cages, lateral lumbar interbody fusion (LLIF)cages, and oblique lumbar interbody fusion (OLIF) cages.

Other embodiments of the disclosure will be apparent to those skilled inthe art from consideration of the specification and practice of thedisclosure provided herein. It is intended that the specification andexamples be considered as exemplary only.

What is claimed is:
 1. An expandable spinal implant, comprising: ahousing comprising an upper plate configured for placement against anendplate of a first vertebral body, and a lower plate configured forplacement against an endplate of a second, adjacent vertebral body; andan integrated ratchet assembly within the housing and being configuredto effect angular adjustment of the spinal implant.